1. Field of the Invention
This invention relates to load restraining and protecting devices, and more particularly to an inflatable load restraining and protecting device capable of operating in changing ambient pressure conditions.
2. Description of the Prior Art
Various cargo and more generally, load protecting devices have been proposed and implemented to protect articles and packages being shipped and transported. Early examples include cartons, small Styrofoam pieces typically referred to as xe2x80x9cpopcornxe2x80x9d packed inside shipping boxes, soft and hard molded Styrofoam, and plastic sheets filled with air pockets commonly known as xe2x80x9cbubble wrapxe2x80x9d. Such packing products are difficult to dispose of and do not readily decompose, resulting in environmental problems. Further, such products are rather time consuming to use, difficult to reuse, and not particularly effective as cargo, such as packages, can shift, fall and crush into other packages and damage both the outer packaging and the inner contents, especially during cargo load shifting during cargo transport. Significant efforts have been focused on solving such problems. For example, U.S. Pat. No. 5,351,829 teaches the use of a plurality of air inflatable components shaped to fit the corners of articles and U.S. Pat. No. 4,918,904 teaches an inflatable pocket having air chambers which are designed to envelop and protect articles contained within the pocket. U.S. Pat. Nos. 4,969,312, 5,803,263, and 5,348,157 disclose inflatable structures inside a container forming an inflatable cushion for coming into close contact with an article to be packaged.
Another genre of load and cargo protecting devices is seen in U.S. Pat. No. 3,782,758 (RE 28,788) where a load retainer utilizes a horizontal rod along which a sheet of material may be moved fore and aft in the container as desired. A similar device is seen in U.S. Pat. No. 4,781,498 showing an adjustable partition for use inside of a transport vehicle.
Another type of cargo or load protecting device is seen in U.S. Pat. No. 5,458,447 where a restraining device for vehicular transport comprises a lattice webbing of straps attached to one another with a plurality of self locking buckles and flat hooks for use in vehicles to restrain cargo loads.
For traditional air inflatable load (such as cargo) cushioning or protecting devices, air bladders can be considered. Generally, pressure bladder systems can be noted in the art of air mattresses. A long-standing problem in air mattress design involves the ability to maintain constant pressure within the air mattress in spite of varying loads on the mattress as one or more users sit or lie on the bed, toss and turn during sleep or arise and return to bed. The xe2x80x9cfeelxe2x80x9d of the mattress to the user is considered to be directly related to the amount of air pressure within the mattress. Thus, in an air mattress into which air is drawn to a certain pressure and then sealed, such as those shown in U.S. Pat. Nos. 3,872,525 and 3,877,092, the internal pressure increases when a user lies thereon and the mattress thus xe2x80x9cfeelsxe2x80x9d harder as the load thereon increases.
U.S. Pat. Nos. 4,224,706 and 4,306,322 disclose air mattress systems which allow the firmness of the mattress to be controlled when a person is lying thereon through the use of a separate bladder which contains a quantity of air adapted to be transferred between the air mattress and the bladder responsive to changes in the volume of the bladder.
Also known are manually operated air mattress systems, such as that shown in U.S. Pat. No. 4,394,784, where air is supplied to a mattress by a blower or vented from the mattress through valves, both the blower and the valves being electronically controlled by hand-held control units. U.S. Pat. No. 4,078,842 discloses an inflatable auto seat wherein pressurized air is supplied by a manually operated compressor. U.S. Pat. No. 3,303,518 discloses an inflatable mattress wherein air is supplied to compartments therein by hoses connected to a remotely located compressor/pump controlled by the user.
U.S. Pat. No. 4,686,722 discloses a mattress formed from a plurality of individual cushions interconnected by ducting to an air pressure source. The pressure in selected cushions may be controlled by computer. U.S. Pat. No. 4,694,520 discloses an air mattress which includes a sensor positioned within the mattress which turns on an air compressor when the mattress deflates to a point where a patient comes in contact therewith. U.S. Pat. No. 4,711,275 discloses a mattress including a rather complex system having a plurality of air compressors and pressure sensors to inflate and deflate portions of the mattress in cycle to prevent bedsores on a bedridden patient.
U.S. Pat. No. 4,679,264 discloses a self-regulating air mattress including a reservoir and means for adding or removing air from the system. A sensing device is disclosed which is adapted to sense the pressure in the mattress and add or remove air therefrom to maintain a constant pressure. Experimentation has shown, however, that such a system, supposedly designed to maintain pressure within a mattress at a predetermined level by sensing pressure and adding or removing air from the mattress in response to a change in pressure, simply does not work to provide effective load support. The problem of such systems is that, assuming a preset pressure to be sensed and maintained, the pressure within the mattress is increased when a load is placed thereon. This increased pressure is sensed and air is vented from the mattress in response thereto. However, venting of air from the mattress does not decrease pressure within the mattress so long as the load remains thereon until the mattress is almost totally deflated.
Inflation indicators for providing a visual indication of when an air bag is in a properly inflated condition are shown in U.S. Pat. Nos. 5,678,969 and 5,730,564. A cargo load dividing apparatus is disclosed in U.S. Pat. No. 6,017,175.
Finally, a combination lattice web and air pressure bladder inflatable cargo load lock is disclosed in U.S. Pat. No. 5,833,413. This prior inflatable cargo load lock includes an air pressure control unit which allows for pressure adjustments responsive to load, temperature and atmospheric changes. More specifically, the air pressure control unit is designed so as to keep a constant pressure in the bladder and on the load being locked. Such design is insufficient in that, similar to the mattress described above, a shifting load which lies on or leans on the bladder will increase the pressure in the bladder. The disclosed air pressure control unit must therefore remove air from the bladder, decreasing bladder volume, to maintain a constant pressure in the bladder and on the load being locked. Ultimately, the bladder may become substantially deflated (having smaller volume with constant pressure both within the bladder and on the lying or leaning cargo) and the cargo, or portions of the cargo, substantially shifted from its initial and intended position(s). More effective, and part of the instant invention, is recognition that maintaining bladder volume at a sufficient restraining force transmitting position respective to the load is essential to provide stable load restraint.
Accordingly, it is a preferred object of this invention to provide an improved load restraint system for limiting movement of a load within a container, using an inflatable bladder which exerts restraining force against the load to restrict unwanted movement.
An additional object of the invention is an improved load restraint system that retains the bladder in essentially constant inflated volume, and under sufficient pressure, to restrain the load when ambient pressure in the container varies.
A further object of the invention includes a web disposed between the bladder and the load to protect the bladder against rupture and/or additionally support the load. Such web may also act as a threshold emergency support for the load if the bladder critically fails.
Another object of the invention includes a web secured within the container and disposed against the bladder remote from its contact with the load to effectively reduce the volume of the container that the inflated bladder must fill to contact the load with restraining force.
Yet another object of the invention includes inflation of the bladder with various fluids having useful properties (such as temperature control) or which may rigidify to form in-situ a structurally rigid load support structure.
Another object of the invention includes the positioning of shaped and/or multiple bladders within the container to provide load support, as for irregularly shaped loads, or as for multiple direction movement force restraint.
A further object of the invention is to provide rapid bladder evacuation capability to permit deflation or partial deflation, as for repositioning or removal of the bladder for access to the load.
These and other objects and advantages of the invention will become apparent in the description and the claims.